Various interfaces and designs have been developed for an operation input unit of a portable electronic apparatus. For example, there is a technique which provides a rotary dial input device to a portable electronic apparatus and moves a cursor displayed on a display unit according to the rotation amount of the rotary dial input device (see Japanese Patent Application Laid Open No. 2003-280792). However, since the conventional technique employs “rotary dial” rotated physically and mechanically, there are troubles or errors caused by mechanical abrasion. Therefore, maintenance of the operation input unit is necessary, and the durable period is short.
In order to solve above problems, techniques employing touch sensor elements, which are not operated by physical and mechanical rotations, in an operation unit have been suggested (see Japanese Patent Application Laid Open Nos. 2005-522797 and 2004-311196). These techniques arrange a plurality of touch sensors annularly to detect a contact, monitor contact detections by touch sensor elements, and when continuous contact detections are detected, it determine there is a movement instruction of a display position according to the movement of contact detection points.